Much like how gifs work, I presume.
Like you just imagine someone shaking their head. Just kine you imagine someone smiling when I type :)
The thing is, shaking ones head isn’t as universal of a symbol as smiling. Some cultures have nods and shakes the other way around. Which seems somewhat weird.
weker01@sh.itjust.works 22 hours ago
It was a figure of writing in old chatrooms and bulletin boards.